高温高压下UH_(3)结构稳定性及其冲击分解

Structural Stability and Shock Decomposition of UH3 at High Temperature and High Pressure

利用统计物理模型构建了UH_(3)晶体及其化学分解产物的状态方程,通过比较Gibbs自由能获得了UH_(3)的高温高压相图,并将其应用于疏松和密实UH_(3)冲击压缩性质研究中。结果表明:等温压缩下,UH_(3)晶体在压力约74.0 GPa时发生化学分解,提高温度有助于化学分解的发生,但压力对UH_(3)化学分解相边界的影响是非单调的;冲击加载下,密实UH_(3)在35~50 GPa压力范围内发生化学分解,并且由于冲击分解伴随着明显的体积塌缩,分解产物的雨贡纽曲线位于等温压缩线下方,曲线位置关系反常;UH_(3)的冲击分解压力随着疏松度的增大而减小,当UH_(3)材料的初始疏松度为1.5时,在化学分解转变压力范围内,UH_(3)的分解产物比UH_(3)晶体更难压缩,表现出类似大疏松度材料在冲击作用下的“反常膨胀”现象。研究结果丰富了对UH_(3)材料动态压缩特性的认识,为锕系金属氢化物的高温高压物理化学性质研究提供了理论参考。

Using statistical physical model,the equation of state of UH_(3) crystal and its chemical decomposition products were constructed in this paper.The phase diagram of UH_(3) at high temperature and high pressure was obtained by Gibbs free energy comparison,and the shock compression properties of UH_(3) with different initial densities were investigated.The results show that the chemical decomposition of UH_(3) crystals occurs at about 74.0 GPa under isothermal compression.Increasing the temperature promotes the chemical decomposition,but the influence of pressure on the chemical decomposition of UH_(3) is nonmonotonic.Solid UH_(3) decomposes at 35–50 GPa under shock compression,and the chemical decomposition process is accompanied by obvious volume collapse,therefore,the Hugoniot of UH_(3) decomposition products lies below the isotherm,which is an abnormal phenomenon in comparison with ordinary metals or compounds.Moreover,the decomposition pressure of UH_(3) decreases with the increase of initial porosity.When the initial porosity is about 1.5,the decomposition products of UH_(3) are more difficult to compress than UH_(3) in crystal phase,thus showing a phenomenon similar to the abnormal expansion of large porosity materials under shock compression.These results enrich our understanding of dynamical compression behavior of UH_(3),and can serve as theoretical basis for further research on physical and chemical properties of actinide metal hydrides at high temperature and high pressure.